Geometric Second Order Field Equations for General Tensor Gauge Fields

Higher spin tensor gauge fields have natural gauge-invariant field equations written in terms of generalised curvatures, but these are typically of higher than second order in derivatives. We construct geometric second order field equations and actions for general higher spin boson fields, and first order ones for fermions, which are non-local but which become local on gauge-fixing, or on introducing auxiliary fields. This generalises the results of Francia and Sagnotti to all representations of the Lorentz group.Comment: 34 pages, LaTeX. Reference adde

Replicate Periodic Windows in the Parameter Space of Driven Oscillators

In the bi-dimensional parameter space of driven oscillators, shrimp-shaped periodic windows are immersed in chaotic regions. For two of these oscillators, namely, Duffing and Josephson junction, we show that a weak harmonic perturbation replicates these periodic windows giving rise to parameter regions correspondent to periodic orbits. The new windows are composed of parameters whose periodic orbits have periodicity and pattern similar to stable and unstable periodic orbits already existent for the unperturbed oscillator. These features indicate that the reported replicate periodic windows are associated with chaos control of the considered oscillators

Tensor gauge fields in arbitrary representations of GL(D,R): II. Quadratic actions

Quadratic, second-order, non-local actions for tensor gauge fields transforming in arbitrary irreducible representations of the general linear group in D-dimensional Minkowski space are explicitly written in a compact form by making use of Levi-Civita tensors. The field equations derived from these actions ensure the propagation of the correct massless physical degrees of freedom and are shown to be equivalent to non-Lagrangian local field equations proposed previously. Moreover, these actions allow a frame-like reformulation a la MacDowell-Mansouri, without any trace constraint in the tangent indices.Comment: LaTeX, 53 pages, no figure. Accepted for publication in Communications in Mathematical Physics. Local Fierz-Pauli programme achieved by completing the analysis of Labastid

A note on spin-s duality

Duality is investigated for higher spin ($s \geq 2$), free, massless, bosonic gauge fields. We show how the dual formulations can be derived from a common "parent", first-order action. This goes beyond most of the previous treatments where higher-spin duality was investigated at the level of the equations of motion only. In D=4 spacetime dimensions, the dual theories turn out to be described by the same Pauli-Fierz (s=2) or Fronsdal ($s \geq 3$) action (as it is the case for spin 1). In the particular s=2 D=5 case, the Pauli-Fierz action and the Curtright action are shown to be related through duality. A crucial ingredient of the analysis is given by the first-order, gauge-like, reformulation of higher spin theories due to Vasiliev.Comment: Minor corrections, reference adde

Recuperação de área degradada com sistema agroflorestal no Vale do Rio Doce, Minas Gerais.

O Vale do Rio Doce, MG, apresenta um histórico de ocupação e uso do solo que favorece a degradação ambiental, em que predominam pastagens sob o uso constante de queimadas. Os sistemas agroflorestais têm se mostrado eficientes na recuperação de áreas degradadas. Neste estudo foram avaliados os efeitos de um sistema agroflorestal na recuperação do solo em área degradada por pastagem na comunidade de Ilha Funda,Município de Periquito, Minas Gerais. A implantação do sistema se deu em 1994 e está sendo conduzido segundo os princípios agroecológicos, potencializando a regeneração natural e a sucessão de espécies. Em 1998, foram coletadas amostras de solo na área em recuperação e em duas áreas adjacentes: uma área degradada, que se encontrava em condições semelhantes às da área em recuperação no início do processo, e outra ocupada por pastagem. Foram determinados atributos químicos do solo e realizada a caracterização da matéria orgânica. O solo da área em recuperação com sistema agroflorestal mostrou-se em melhores condições do que o solo sob pastagem e o da área degradada, apresentando maior dinâmica do carbono orgânico e maior disponibilidade de nutrientes. Embora o teor de carbono orgânico total apresentado pelo solo sob pastagem tenha sido maior que nas demais condições avaliadas, o solo do sistema agroflorestal já está se igualando ao da pastagem no acúmulo das formas mais estáveis de carbono e apresentando maior dinâmica das frações orgânicas menos estáveis. Este estudo comprovou a eficiência dos sistemas agroflorestais, conduzidos segundo os princípios agroecológicos, na recuperação de áreas degradadas

Quantification of milk adulterants (starch, H2O2, and NaClO) using colorimetric assays coupled to smartphone image analysis

In this paper, a colorimetric method for the detection of milk adulterants using smartphone image analysis is reported. This is based on the reactions to detect hydrogen peroxide, sodium hypochlorite, and starch in milk, where a color variation is observed for each substance. The image analysis was performed by using lab-made apps (PhotoMetrix®, and RedGIM®) based on partial least squares regression with the histograms of the red-green-blue images. The image histograms are automatically calculated using the smartphone camera and processed within the app. The results have shown the capability of this method to predict the concentration of the three adulterants, demonstrating the potential of the use of digital images and smartphone applications associated with chemometric tools. This method presents a fast, low-cost, and portable way to quantify adulterants in Cow milk